They did more than that. The Federal Goverment owns most of the mineral rights AND most of the surface in Alaska. The State Goverment owns a much smaller but significant portion, about 28%. The natives were awarded about 11% of the land and mineral rights. Private ownerships of land is Alaska is less than 1% of the state.
Land Ownership in Alaska, with map
http://www.conservationgiscenter.org/maps/html/landown.html
The federal ownership of the land and mineral rights is the reasons most of the oil in Alaska is NOT being produced. The majority of the oil production in Alaska is on the state owned land and native land where oil exploration and production is typically encouraged. Federal Lands include the coastal plain of ANWR, that was specifically set aside to be explored for oil production but has been held up.